Angiography is a medical imaging technique to image blood vessels and blood vessel systems, and can be used for example to enable diagnostics, surgical planning, and simulation.
Angiographic image data can be generated by injecting a contrast agent intravenously to a patient and scanning the patient using e.g. Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). The resulting angiographic image data is typically a set of DICOM-images forming a voxel volume with discrete image intensities. The voxel volume can be processed to segment organs, blood vessels, skeleton etc. In particular, the segmentation and further characterization can provide a segmented surface that delimits the blood vessel or vessel system from other tissues.
An example of such a characterization method for characterizing a vascular system in a three-dimensional angiographic image comprised of voxels is disclosed in U.S. Pat. No. 6,842,638. Here a two-dimensional slice formed of pixels is extracted from the angiographic image. Imaged vascular structures in the slice are located and flood-filled. The edges of the filled regions are iteratively eroded to identify vessel centres. The extracting, locating, flood-filling, and eroding is repeated for a plurality of slices to generate a plurality of vessel centres that are representative of the vascular system. A vessel centre is selected, and a corresponding vessel direction and orthogonal plane are found. The vessel boundaries in the orthogonal plane are identified by iteratively propagating a closed geometric contour arranged about the vessel centre. The selecting, finding, and estimating are repeated for the plurality of vessel centres, and the estimated vessel boundaries are then interpolated to form a vascular tree.
However, sometimes a portion of the boundary of a blood vessel may be “missing”, or not discernable, such that the boundary does not continuously enclose the blood vessel in the dimensional slice. If so, the flood-filling procedure will fail as it expands outside the blood vessel. This makes the method suggested in U.S. Pat. No. 6,842,638 sensitive to imperfections in the DICOM-image. Thus, there is a need for a more robust method to characterize a blood vessel.